Chandra Spacecraft Gives Dynamic Look At Milky Way

January 10, 2002|By John Nobel Wilford The New York Times

WASHINGTON — Peering deep into the heart of the Milky Way with X-ray vision, an American spacecraft has produced what astronomers say is the sharpest-ever image of the most dynamic region of Earth's home galaxy.

A team of astronomers led by Dr. Q. Daniel Wang of the University of Massachusetts at Amherst reported on Wednesday that NASA's Earth-orbiting Chandra X-ray Observatory had detected more than 1,000 discrete sources of the powerful X-rays, far more than the dozen sources previously known.

"This is an important step toward understanding the most active region of our galaxy," Wang said at a meeting of the American Astronomical Society. "It gives us a new perspective of the interplay of stars, gas, dust and gravity at the very epicenter of the galaxy."

Until the advent of X-ray spacecraft, especially Chandra, such a detailed examination of the Milky Way's core had been impossible, since most of it is obscured in a smog of gas and dust. By penetrating this smog, scientists said, the new research could lead to insights into what is happening at the centers of other galaxies.

The Chandra images cover a region 400 light years wide by 900 light years long, in the galactic suburbs about 20,000 light years away from the sun.

If someone in the Northern Hemisphere looked at the broad, glittering arc of the Milky Way in the summer, its center would be close to the southern horizon. The best view at all times is from the Southern Hemisphere.

But the X-ray images reveal phenomena unseen in other wavelengths, even by the most powerful ground-based telescopes.

In their analysis of the new observations, Wang and his colleagues -- Dr. Cornelia Lang, also of the University of Massachusetts, and Dr. Eric Gotthelf of Columbia University -- determined that most of the discrete X-ray sources were from remnants of dead stars, like white dwarfs, neutron stars and black holes.

The astronomers, however, could add little new about the huge black hole, with a mass 3 million times that of the sun, that has been detected at the galactic core.

Chandra recently observed a small flare from the vicinity of the black hole, an extremely dense object with gravity so powerful than light cannot escape it.